In electronically controlled switching systems, a defined number of subscriber lines or trunks are often combined into a group and are controlled by what is referred to as a group processor. The required group processor performance is roughly proportional to the number of subscriber lines or trunks and can be calculated from empirical values (for example, number of call attempts per time unit and subscribers).
There is no longer any fixed relationship between the number of terminals and the group processor performance required for that purpose in broad band switching systems, particularly ATM switching systems having greatly different bit rates per connection. For example, only one broad band connection per hour could be set up via a 155 Mbit/s subscriber line, but thousands of speech connections per hour could be set up via another such subscriber line, i.e. the group processor performance required per terminal (port) can fluctuate by more than three orders of magnitude.